ΔE 20.8, loose: different enough that you should pick on purpose. Cobalt Blue is a little lighter, much more saturated than Kantor Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Cobalt Blue is a little lighter, much more saturated than Kantor Blue.
The same difference applies the other way round: Kantor Blue is a little darker, much more muted.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Kantor Blue on the colour wheel See Cobalt Blue on the colour wheel
All matches: Kantor Blue equivalents · Cobalt Blue equivalents